Effects of ultrasonic treatment and storage temperature on egg quality

Effects of ultrasonic treatment and storage temperature on egg quality

PROCESSING, PRODUCTS, AND FOOD SAFETY Effects of ultrasonic treatment and storage temperature on egg quality D. Sert,*1 A. Aygun,† and M. k. Demir* *F...

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PROCESSING, PRODUCTS, AND FOOD SAFETY Effects of ultrasonic treatment and storage temperature on egg quality D. Sert,*1 A. Aygun,† and M. k. Demir* *Faculty of Agriculture, Department of Food Engineering; and †Faculty of Agriculture, Department of Animal Science, Selcuk University, Konya, 42075, Turkey specific gravity, shell strength, albumen height, and Haugh unit were observed in ultrasonic-treated eggs. The egg quality was significantly improved with ultrasonic treatment (P < 0.01). The total mesophilic aerobic bacteria values of yolk and albumen decreased with increase in ultrasonic treatment time from 5 to 30 min. Ultrasonic treatment improved the sensory properties of egg shells.

Key words: egg quality, ultrasonic treatment, storage temperature, Haugh unit, egg shell 2011 Poultry Science 90:869–875 doi:10.3382/ps.2010-00799

INTRODUCTION

vegetables, egg shells, and food packages (Shoh, 1988, Floros and Liang, 1994; Mizrach et al., 1994). Applications also include direct process improvements such as cleaning surfaces, enhancement of dewatering, drying and filtration, inactivation of microorganisms and enzymes, disruption of cells, degassing of liquids, acceleration of heat transfer and extraction processes, and enhancement of any process dependent upon diffusion (Floros and Liang, 1994). No previous study analyzes the quality of eggs after the shell is exposed to the ultrasonic process. A process such as the application of an ultrasonic treatment could preserve the internal freshness of eggs by sealing pores and thus reducing the mass transfer of gas and moisture. The storage time for shell eggs could therefore be increased. A protective treatment could also improve shell strength to some extent. Therefore, ultrasonic treatment could provide similar benefits to using barrier packaging and significantly reduce the number of eggs lost.

Eggs are perishable and can rapidly undergo weight loss and interior quality deterioration during storage, causing a major economic loss to the poultry industry (Freeland-Graves and Peckman, 1987; Caner, 2005; No et al., 2005). Losses to the egg industry as a result of problems related to egg and egg shell quality have been estimated to be in excess of $10 million annually (Wong et al., 1996). Increase of albumen pH, the thinning of the albumen, and the evaporation of water through the shell are well-known phenomena during the storage of the eggs (Mara et al., 1996). Egg albumen also undergoes a liquefaction process during storage. The thinning of the thick albumen, an important indicator of interior quality, is caused by the change in the albumen pH from approximately 7.5 to approximately 9.6. The increase in pH is a result of carbon dioxide loss through pores in the shell (Mara et al., 1996; Caner, 2005). Ultrasound technology has wide range of applications in food processing. These applications include texture, viscosity, and concentrations measurements of solid or fluid foods; composition determination of liquid eggs, meats, fruits, vegetables, dairy products, and others products; thickness, flow level, and temperature measurements for monitoring and control of some processes; and nondestructive control of whole fruits and

MATERIALS AND METHODS Sampling and Storage A total of 120 unwashed, feces-free, white shell, medium (60–75 g), fresh eggs were obtained from Lohmann LSL Classic laying hens (80 wk of age) that were raised on the Research and Application Farm of Selcuk University (konya, Turkey). The hens were fed a layer ration (Table 1). All eggs were collected in a 24-h period. Before the ultrasonic treatments, eggs were stored for 1

©2011 Poultry Science Association Inc. Received March 24, 2010. Accepted January 8, 2011. 1 Corresponding author: [email protected]

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ABSTRACT In this study, the effects of ultrasonic treatment and storage temperature on egg weight, specific gravity, shell strength, albumen height, Haugh unit, color, pH, water activity, total mesophilic aerobic bacteria, mineral content, and sensory properties were investigated. Ultrasonic treatment was used to improve egg properties. The lowest weight loss values were obtained with eggs treated with 15 min of ultrasonic treatment and stored at 5°C for 10 d. The higher

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d at room temperature (20 ± 2°C). Eggs were stored for 10 d at 5 and 22°C after the ultrasonic treatments.

is the albumen height (mm) and W is the weight of egg (g; Monira et al., 2003).

Ultrasonic Equipment and Treatments

pH Measurement

For ultrasonic treatment, an ultrasonic bath (Sonorex RK 100 H, Bandelin, Berlin, Germany) with 140 W of power and 35 kHz frequency was used. Eggs were sunk into an ultrasonic bath filled with ultrapure water (Human UP 900, Hanna Tech. Co., Soeul, Korea; pH, 7.0; mineral content, <1 µg/kg). Eggs were treated with ultrasonic wave for 5, 15, and 30 min at 30°C. Treatments were no ultrasound (C), 35 kHz for 5 min (U5), 35 kHz for 15 min (U15), and 35 kHz for 30 min (U30).

After the eggs were broken, the albumen was separated from the yolk. After diluting the sample with 9 vol of deionized distilled water, the pH of the egg yolk or white was measured using pH meter with Sentix 42 electrode (pH 315i/SET WTW, Weilheim, Germany).

Analytical Methods

Table 1. Composition of the diet Item (% unless noted)

Amount

Ingredient   Corn, yellow   Soybean meal, 48%   Sunflower meal, 28%   Wheat bran   Limestone   Dicalcium phosphate   Salt   dl-Methionine   Vitamin premix1   Mineral premix2   Vegetable oil   Total Calculated value   CP   ME (kcal/kg)   Crude fiber   Ca   Available P   Lysine   Methionine + cystine   Threonine   Tryptophan

62.55 15.20 7.73 3.06 8.70 1.28 0.15 0.08 0.15 0.10 1.00 100   15.90 2,750 3.07 3.70 0.35 0.80 0.61 0.67 0.21

1Vitamin

premix supplied per kilogram of diet: vitamin A, 8,800 IU; vitamin D3, 2,200 IU; vitamin E, 13 IU; vitamin K3, 2.67 mg; vitamin B1, 2.5 mg; vitamin B2, 4.67 mg; vitamin B6, 3.33 mg; calcium d-pantothenate, 8.8 mg; nicotine acid, 44 mg; d-biotin, 0.11 mg; folic acid, 1.0 mg; vitamin B12, 6.6 mg. 2Mineral premix supplied per kilogram of diet: Cu, 5 mg; Fe, 60 mg; Mn, 100 mg; Zn (ZnO), 60 mg; Se, 0.15 mg; Co, 0.50 mg; choline, 125 mg.

Water activity (Aw) measurements were performed with an Aqualab apparatus (Model Series 3TE, Decagon Devices Inc., Pullman, WA). Pure water (1.000 ± 0.003%) was used as standard for equipment calibration.

Microbiological Analysis The outer surface of the egg shell was disinfected with 70% ethanol and air dried. After the disinfection process, the air pocket was opened and the yolk and albumen were separated with sterile scissors and forceps in aseptic conditions. Egg samples were measured in sterile stomacher bags aseptically (10 g) and homogenized with the addition of 90 mL of 0.1% peptone water (Merck, Darmstadt, Germany) 90 s before the analysis by stomacher to obtain further dilution. Total mesophilic aerobic bacteria (TMAB) was enumerated on standard plate count agar (Merck) after incubation at 30°C for 48 h. After incubation, plates with 3 to 300 colonies were counted, and the results were expressed as a logarithm of colony forming units per gram (AOAC, 1995).

Color Measurements Color measurement was performed using a Minolta Chroma Meter CR-400 (Minolta, Osaka, Japan). The light–dark chromaticity (L*), green–red chromaticity (a*), and blue–yellow chromaticity (b*) color measurements were determined according to the CIELab color space system. The instrument was calibrated with a white reference tile (L* = 97.10, a* = −4.88, b* = 7.04) before the measurements (Francis, 1998). Each measurement was repeated more than 3 times and average values were reported.

Analysis of Minerals In the analysis of minerals, a microwave system (MARS 5, CEM Corporation, Matthews, NC) was used for acid digestion of all the samples. Samples were prepared in triplicate runs (CEM Corporation, 1998). Mineral concentrations (mg/100 g) were determined by inductively coupled plasma atomic emission spectrometry (CCD Simultaneous ICP-AES, Varian, Palo Alto,

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Egg weight was measured using a balance and was recorded to the nearest 0.01 g. Specific gravity was estimated by Archimedes’ method (Wells, 1968). Shell strength (kg) was measured with an Egg Force Reader (06-UM-001, Version B, Orka Food Tech. Ltd., Hong Kong, China). The height of the albumen was measured using an EggAnalyzer (05-UM-001, Version B, Orka Food Tech. Ltd.). The Haugh units were calculated using the Haugh unit calculator, converting egg weight and albumen height values to Haugh units. The formula for calculating the Haugh unit is as follows: Haugh unit = 100 log (H − 1.7W0·37 + 7.6), where H

Water Activity Measurement

EFFECTS OF ULTRASONIC TREATMENT ON EGG QUALITY

CA) with an automatic sampler system. Plasma conditions were as following; power, 1,400 W; gas exit, 13.50 L/min; gas flow rate, 1.50 mL/min; nebulizer gas flow rate, 0.90 mL/min; sample intake rate, 2.25 mL/min; preflow time, 45 s; reading time, 3 × 24 s.

Sensory Analysis Sensory properties were evaluated using a hedonic scale for sensory evaluation of eggs by 60 panelists. A 9-point hedonic scale was used with 1 = dislike extremely, 5 = neither like nor dislike, and 9 = like extremely. Each panelist was asked to evaluate the egg groups in terms of surface smoothness, surface glossiness, odor, stickiness, and general acceptability (Caner, 2005).

Costat software (Costat, 1990) was used to perform the statistical analyses. Differences in samples as a result of ultrasonic treatment and storage temperature were tested statistically. Duncan’s multiple range tests was used to differentiate between the mean values. Standard deviations were calculated using the same software.

RESULTS AND DISCUSSION Egg Quality Table 2 lists the eggs used in this study and shows the egg weight, specific gravity, shell strength, albumen height, and Haugh units. No significant difference was found between treatments for egg weight at the beginning of the experiment. When the eggs were stored for 10 d at 5°C, the C treatment had lower weight than the others, which did not differ. When stored for 10 d at 22°C, the eggs of the C and U5 treatments had lower weights when compared with the others. Eggs stored for 10 d (regardless of storage temperatures) showed lower weight compared with fresh eggs. Figure 1 shows egg weight loss. The lowest weight loss values were obtained with eggs that were ultrasonically treated for 15 min and stored for 10 d at 5°C, and the highest values were obtained with eggs that were ultrasonically treated for 5 min and stored for 10 d at 22°C. Specific gravity was affected by storage time and temperature; it was higher for fresh eggs compared with eggs stored for 10 d at 5 and 22°C. However, no significant differences were observed between treatments. Shell strength was higher with eggs stored for 10 d at 5°C compared with eggs stored for 10 d at 22°C and fresh eggs. No significant difference was found between treatments at the beginning of the experiment and eggs stored for 10 d at 22°C. Significant difference was found between treatments stored for 10 d at 5°C; C treatment was lower than the U5, U15, and U30 treatments. The values of albumen height significantly decreased with storage time and temperature. The higher albumen height was

determined for fresh eggs at the beginning of experiment. Albumen height of eggs stored for 10 d at 5°C was higher than for eggs stored at 22°C. The U30 eggs had higher albumen height than the eggs stored for 10 d at 22°C, but no significant differences were observed between treatments in fresh eggs and the eggs stored for 10 d at 5°C. The decreasing rate of the thick albumen height at room temperature was much higher than that at refrigerator temperature. This indicates that temperature is one of the main factors influencing egg quality during storage. The liquefaction of the thick white is largely influenced by the storage temperature. Haugh units were affected by the storage time and temperature. The eggs stored for 10 d at 22°C had lower Haugh units than the eggs stored for 10 d at 5°C and eggs at the beginning of the experiment. No significant differences were found between eggs at the beginning of the experiment and eggs stored for 10 d at 5°C, but higher Haugh units were found in the U30 treatment compared with C and U5 treatments when the eggs were stored for 10 d at 22°C. Similar results have been reported by Alleoni and Antunes (2004). These results agreed with the previous study of Wong et al., (1996), who reported that the Haugh unit values ranged from 35 to 52 for eggs coated with gluten, mineral oil, and soybean protein isolate. The higher Haugh unit value (72) was reported by Oliveira (1992). Ultrasonic treatment reduced weight loss and preserved the albumen and yolk quality. The higher specific gravity, shell strength, albumen height, and Haugh unit values observed in ultrasonically treated eggs showed that egg quality was significantly improved with ultrasonic treatments. The effects of storage time and temperature on albumen quality are well documented (Stadelman and Cotterill, 1995). Albumen height and Haugh units decrease with storage time, and this decrease occurs more quickly at higher temperatures. Rapid cooling of eggs with carbon dioxide was found to improve Haugh units of stored eggs (Keener et al., 2000). The changes occurring in albumen quality during egg storage appear to be related to changes occurring in ovomucin, particularly the thick albumen (Kato et al., 1981; Toussant and Latshaw, 1999). During egg storage, the quality of the vitelline membrane declines, making the yolk more susceptible to breaking (Kirunda and McKee, 2000).

Albumen and Yolk Quality Changes in the yolk and albumen properties at different ultrasonic treatment times and different storage temperatures are noted in Table 3. Changes in pH, Aw, and TMAB values of both yolk and albumen are indicated in Table 3. The pH of the yolk and albumen after storage for 10 d at 22°C was higher than that after storage for 10 d at 5°C and in fresh eggs. No significant differences existed between treatments for yolk and albumen pH, irrespective of the storage time and temperature. The significantly higher albumen pH and lower albumen height found in eggs stored for 10 d in-

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Statistical Analysis

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Figure 1. Effects of storage temperature on weight loss of stored eggs. C = no ultrasound; U5 = ultrasonic treatment for 5 min at 35 kHz; U15 = ultrasonic treatment for 15 min at 35 kHz; U30 = ultrasonic treatment for 30 min at 35 kHz.

The TMAB values of yolk and albumen were affected by storage time and temperature. The lowest TMAB of yolk and albumen was observed in eggs stored for 10 d at 5°C. Significant differences were found in TMAB values between the beginning of the experiment, after storage for 10 d at 5°C, and after storage for 10 d at 22°C. At the beginning of the experiment, the lowest yolk and albumen TMAB values were observed in eggs treated with U30. When stored for 10 d at both 5 and 22°C, the U30-treated eggs had lower TMAB values than the other eggs. Significant differences existed between treatments for albumen TMAB in fresh eggs (at the beginning of the experiment) and after storage for 10 d at 5°C. The lowest albumen TMAB value was observed in U30-treated eggs regardless or storage time and temperature. The C treatment was not significantly different from the U5 treatment, but was significantly different from the U15 treatment. Different in-shell

Table 2. Effects of ultrasonic treatment and storage temperature on egg quality Storage time and temperature

Ultrasonic treatment1

0d

C U5 U15 U30 Mean (±SD) C U5 U15 U30 Mean (±SD) C U5 U15 U30 Mean (±SD)

10 d, 5°C

10 d, 22°C

a,bWithin

Egg weight (g)

Specific gravity (g/cm3)

Shell strength (kg)

Albumen height (mm)

Haugh unit

65.57* 69.52 71.58 74.47 70.29A (5.06) 62.96b 67.94a 70.43a 71.46a 68.20B (4.74) 63.63b 63.95b 68.27a 70.68a 66.63B (3.51)

1.074* 1.079 1.080 1.083 1.079A (0.005) 1.062* 1.063 1.064 1.065 1.064B (0.003) 1.033* 1.037 1.046 1.059 1.044C (0.012)

3.629* 3.683 4.077 4.158 3.887B (0.365) 3.466b 4.201a 4.368a 4.603a 4.160A (0.507) 3.410* 3.656 4.018 4.132 3.804C (0.452)

4.83* 5.13 5.63 5.67 5.32A (0.59) 4.60* 4.80 5.30 5.63 5.08B (0.55) 2.73b 2.93b 3.13b 3.57a 3.09C (0.35)

58.98* 67.76 70.54 72.10 67.34B (6.90) 63.00* 64.81 69.78 73.52 67.78A (5.96) 34.79b 39.52b 40.58ab 49.93a 41.21C (6.49)

storage temperature, values with the same superscript do not significantly differ (P < 0.01). within a column with the same superscript do not significantly differ (P < 0.01). 1C = no ultrasound; U5 = ultrasonic treatment for 5 min at 35 kHz; U15 = ultrasonic treatment for 15 min at 35 kHz; U30 = ultrasonic treatment for 30 min at 35 kHz. *NS. A–CMeans

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dicated that the blastoderm was capable of influencing rate of albumen liquefaction. Storage temperature and ultrasonic treatment increased the albumen pH. Albumen pH ranged from 8.60 to 9.36. Similar results have been reported by some researches (Walsh et al., 1995; Ahn et al., 1999; Alleoni and Antunes, 2004). During storage, some well-known physical and chemical modifications that take place are the thinning of the thick albumen (Kato et al., 1981) and the increase of albumen pH caused by the loss of carbon dioxide from the egg through the pores in the shell (Hill and Hall, 1980). Albumen pH increases with the loss of carbon dioxide from the egg. Carbon dioxide migration from the egg results in an increase in albumen pH; this phenomenon is caused by the deterioration of the gelatinous structure of the albumen. During storage of eggs, the pH of the albumen increases; this is thought to be related to the deterioration of albumen quality. Exposure of fresh broiler eggs to varying concentrations of ammonia resulted in a significant linear relationship between pH and albumen height (Benton and Brake, 2000). Figures 2 and 3 show the albumen and yolk Aw. The Aw value of both yolk and albumen decreased with increasing storage time and temperature. The lowest Aw values of yolk and albumen were determined in eggs stored for 10 d at 22°C. The U30 treatment resulted in lower yolk Aw values than the C treatment at the beginning of the experiment. However, no significant differences were observed between treatments on Aw values after storage for 10 d at either 5 or 22°C. Significant differences were found between treatments on albumen Aw values at the beginning of the experiment. The U30 treatment resulted in the lowest albumen Aw value of the treatments at the beginning of the experiment. The U30 treatment induced lower albumen Aw values than the C treatment for eggs stored for 10 d at either 5 or 22°C.

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EFFECTS OF ULTRASONIC TREATMENT ON EGG QUALITY

Figure 3. Effects of storage temperature on yolk water activity of stored eggs. Black bars: 0 d; gray bars: eggs stored 10 d at 5°C; dotted bars: eggs stored 10 d at 22°C. Values of the same storage temperature with the same letters are not significantly different (P < 0.01). C = no ultrasound; U5 = ultrasonic treatment for 5 min at 35 kHz; U15 = ultrasonic treatment for 15 min at 35 kHz; U30 = ultrasonic treatment for 30 min at 35 kHz.

treatments to reduce bacterial load on the surface or inside shell eggs have been attempted with varying success. Gamma irradiation of shell eggs with increasing radiation doses has demonstrated that a minimal dose of 1.5 kGy is required for the inactivation of Salmonella and other nonpathogenic bacteria (Meszaros et al., 2006). The microwave heating of shell eggs provides an opportunity for significant improvement of the current immersion pasteurization that involves heating the eggs in a water bath at 60°C for about 20 to 25 min (Dev et al., 2008).

by ultrasonic treatment. This increase was not significant at the beginning of application and for the eggs stored at 5°C for 10 d (P < 0.01). The lowest yolk L* values were determined for the eggs stored at 22°C for 10 d. The ultrasonic treatment time did not affect the a* values of yolks. The mean L* and a* values of yolks decreased by the temperature change and storage. The b* values of yolks, which were subjected to ultrasonic waves, were higher than the values of C samples. The C samples showed brighter albumen values. The U30 albumens had the lowest L* values (P < 0.01). The a* values of albumens from samples stored at 5°C for 10 d increased depending on the ultrasonic treatment time. The b* values of albumens of the U30 group were lower than the values of C samples depending on storage temperature, whereas there no significant differences were found between the other groups.

Yolk and Albumen Color Table 4 provides information on the yolk and albumen color of the eggs. The L* values of yolk increased

Table 3. Effects of ultrasonic treatment and storage temperature on yolk and albumen quality1 Yolk Storage time and temperature

Ultrasonic treatment2

0d

C U5 U15 U30 Mean (±SD) C U5 U15 U30 Mean (±SD) C U5 U15 U30 Mean (±SD)

10 d, 5°C

10 d, 22°C

a–dWithin

Albumen

pH

Aw

TMAB (log cfu/g)

pH

Aw

TMAB (log cfu/g)

6.15* 6.08 6.08 6.06 6.09C (0.06) 6.22* 6.21 6.16 6.15 6.19B (0.05) 6.32* 6.28 6.25 6.23 6.27A (0.06)

0.985a 0.983ab 0.983ab 0.981b 0.983A (0.002) 0.981* 0.981 0.980 0.980 0.980B (0.000) 0.976* 0.976 0.974 0.973 0.975C (0.001)

2.565a 2.507b 2.445c 2.403d 2.480B (0.066) 2.450a 2.388b 2.361b 2.292c 2.373C (0.061) 2.610a 2.570a 2.507b 2.422c 2.527A (0.076)

8.33* 8.60 8.66 8.78 8.59C (0.33) 9.08* 9.09 9.11 9.13 9.10B (0.04) 9.32* 9.33 9.38 9.40 9.36A (0.05)

0.988a 0.986a 0.986a 0.983b 0.985A (0.002) 0.987a 0.985ab 0.983b 0.983b 0.984B (0.002) 0.982a 0.979ab 0.976bc 0.975c 0.978C (0.003)

2.604a 2.579b 2.542c 2.485d 2.552B (0.048) 2.530a 2.482b 2.418c 2.344d 2.443C (0.075) 2.769a 2.733ab 2.692b 2.610c 2.701A (0.064)

storage temperature, values with the same superscript do not significantly differ (P < 0.01). within a column with the same superscript do not significantly differ (P < 0.01). 1A : water activity; TMAB: total mesophilic aerobic bacteria. w 2C = no ultrasound; U5 = ultrasonic treatment for 5 min at 35 kHz; U15 = ultrasonic treatment for 15 min at 35 kHz; U30 = ultrasonic treatment for 30 min at 35 kHz. *NS. A–CMeans

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Figure 2. Effects of storage temperature on albumen water activity of stored eggs. Black bars: 0 d; gray bars: eggs stored 10 d at 5°C; dotted bars: eggs stored 10 d at 22°C. Values of the same storage temperature with the same letters are not significantly different (P < 0.01). C = no ultrasound; U5 = ultrasonic treatment for 5 min at 35 kHz; U15 = ultrasonic treatment for 15 min at 35 kHz; U30 = ultrasonic treatment for 30 min at 35 kHz.

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Table 4. Effects of ultrasonic treatment and storage temperature on yolk and albumen color1 Yolk color Storage time and temperature

Ultrasonic treatment2

0d

C U5 U15 U30 Mean (±SD) C U5 U15 U30 Mean (±SD) C U5 U15 U30 Mean (±SD)

10 d, 5°C 

10 d, 22°C 

Albumen color

L*

a*

b*

L*

a*

b*

60.27* 60.31 60.33 61.88 60.70A (1.14) 56.12* 56.64 56.81 58.22 56.95B (2.30) 55.39b 56.62ab 56.87ab 58.14a 56.76C (1.20)

0.47b 0.71a 1.61a 1.90a 1.17A (0.64) 0.51* 0.97 0.93 1.45 0.97B (0.74) 0.48* 0.56 0.96 1.10 0.78C (0.50)

37.25* 36.70 36.71 36.53 36.80C (1.10) 41.23a 38.10ab 37.89ab 35.42b 38.16B (2.64) 51.04a 43.21b 42.58b 40.46b 44.32A (4.82)

40.56a 35.35b 34.82b 31.57c 35.58A (3.49) 37.64a 36.22ab 34.46b 33.66b 35.49A (2.00) 38.76a 33.96ab 33.23ab 30.04b 34.00B (3.77)

0.64* 0.11 −0.49 −0.54 −0.07A (1.11) 0.50a 0.41a −0.44c −1.89b −0.36B (1.02) −0.26* −0.32 −0.50 −1.04 −0.53C (0.69)

15.32a 13.99ab 12.84ab 9.80b 12.98C (2.33) 19.73a 17.42ab 14.36b 14.23b 16.44A (2.58) 17.15a 17.37a 16.70a 13.58b 16.20B (1.87)

a–cWithin

Mineral Amounts The changes in mineral element concentrations in albumen and yolk samples as a result of ultrasonic treatment are given in Table 5. Depending on ultrasonic treatment time, Cu, K, and Na showed decreasing trend; conversely, Ca, Mg, and P concentrations increased. Similar results were obtained for egg yolks. The Fe, Mn, and Zn concentrations of albumens were not affected by ultrasonic application. The Ca, Fe, Mg, Mn, Na, P, and Zn contents of the egg yolk samples also showed a significant (P < 0.01) upward trend within the period of ultrasonic treatment. The Cu and K contents of egg yolk samples significantly (P < 0.01) decreased through ultrasonic treatment. Caner and Cansiz (2007) reported that Ca, Fe, Mg, and Mn of the egg yolks significantly decreased when coated with different components. Tekinsen and Celik (1995) reported that eggs contain most of the Ca, Fe, P, Na, K, Cl, Cu, I,

Mg, and Mn, and the egg yolk contains more Na, K, S, and Cl than the egg albumen.

Sensory Analysis The sensory properties of egg shell samples are presented in Table 6. Significant differences (P < 0.01) were observed in the surface smoothness, surface glossiness, surface odor, surface stickiness, and general acceptability of egg shell samples with ultrasonic treatment period. All sensory properties of egg shell samples increased with increasing ultrasonic treatment time. No visible cracks or deformations on the shell surface were observed with ultrasonic treatment. From a consumer standpoint, safety is an implicit quality attribute of food. Thus, to maintain consumer confidence, food suppliers have the responsibility to make every effort to guarantee health and quality. When trying to reduce

Table 5. Effects of ultrasonic treatment on albumen and yolk mineral content1 Albumen Mineral (mg/100 g) Ca Cu Fe K Mg Mn Na P Zn a–dBetween

C 7.65c

0.025a 0.013a 161.1a 12.39d 0.004a 208.2a 14.6d 0.006a

Yolk

U5

U15

7.69c

8.08b

0.023a 0.013a 150.4b 12.64c 0.003a 203.5b 18.8c 0.007a

0.020b 0.012a 136.8c 13.21b 0.003a 194.6c 25.5b 0.007a

U30

C

U5

U15

U30

10.29a

72.17d

89.66c

90.51b

100.37a 0.128a 3.026a 74.6d 13.55a 0.141a 89.2a 454.1a 3.908a

0.020b 0.012a 124.4d 14.44a 0.003a 185.0d 32.6a 0.007a

0.114c 2.647d 128.9a 12.79d 0.121c 73.7d 418.5b 2.758d

0.117b 2.755c 103.1b 13.23c 0.127bc 78.6c 426.8b 3.614c

0.119b 2.910b 99.4c 13.39b 0.134ab 85.8b 445.8a 3.876b

albumen and yolk, values with the same superscript do not significantly differ (P < 0.01). = no ultrasound; U5 = ultrasonic treatment for 5 min at 35 kHz; U15 = ultrasonic treatment for 15 min at 35 kHz; U30 = ultrasonic treatment for 30 min at 35 kHz. 1C

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storage temperature, values with the same superscript do not significantly differ (P < 0.01). within a column with the same superscript do not significantly differ (P < 0.01). 1L*: light–dark chromaticity; a*: green–red chromaticity; b*: blue–yellow chromaticity. 2C = no ultrasound; U5 = ultrasonic treatment for 5 min at 35 kHz; U15 = ultrasonic treatment for 15 min at 35 kHz; U30 = ultrasonic treatment for 30 min at 35 kHz. *NS. A–CMeans

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EFFECTS OF ULTRASONIC TREATMENT ON EGG QUALITY Table 6. Effects of ultrasonic

treatment1

on sensory acceptability of egg shells

Item Surface smoothness Surface glossiness Surface odor Surface stickiness General acceptability

C

U5

U15

U30

4.5c 5.3c 4.9d 5.6d 5.0d

5.7bc 6.0bc 6.2c 6.3c 5.9c

6.5ab 7.2ab 7.2b 6.9b 6.8b

7.4a 7.6a 7.9a 7.6a 7.4a

a–dBetween

ultrasonic treatments, values with the same superscript do not significantly differ (P < 0.01). = no ultrasound; U5 = ultrasonic treatment for 5 min at 35 kHz; U15 = ultrasonic treatment for 15 min at 35 kHz; U30 = ultrasonic treatment for 30 min at 35 kHz. 1C

the risk of microbiological hazard in egg consumption, ultrasonic treatment can be accomplished.

ACKNOWLEDGMENTS

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The authors thank the Scientific Research Projects (SU-BAP) of Selcuk University Coordinating Office (Konya, Turkey) for financial support.

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